1. Field of the Invention
The present invention relates to an inkjet recording ink, an inkjet recording ink set, and an ink cartridge.
2. Description of the Related Art
Inkjet printers employing inkjet recording methods are compact and inexpensive and form color images in a simple manner, and thus have rapidly been becoming popular. In recent years, there has been a requirement for printing high-quality images at high speed. In order to meet this requirement, inks used for inkjet recording methods have to satisfy various characteristics. Especially when high-speed printing is performed, it is important to suppress color bleeding of ink on recording media or maintain jetting stability of ink good. Degradation in jetting stability is mainly caused by dryness or bubbling of the ink in nozzles, and thus it is necessary to improve this phenomenon.
In view of this, as an ink set that does not cause color bleeding on not only plain paper but also coated paper inferior in water absorbability, there has been proposed an ink set containing a black ink and color inks other than the black ink, where the black ink and the color inks use different water-soluble organic solvents, and the water-soluble organic solvent of the color inks is higher in surface tension than the water-soluble organic solvent of the black ink (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2007-146135).
However, this proposal does not disclose any of combination and ratio of the water-soluble organic solvents that achieve all of less color bleeding, good color saturation and good jetting stability.
Also, there has been proposed an inkjet recording ink excellent in, for example, image clarity, jetting stability and ink storageability, which contains, as a dispersing agent, a compound represented by the following General Formula (1) or a naphthalene sulfonic acid-formalin condensate (see, for example, JP-A Nos. 2006-045436 and 2009-235233).

In the General Formula (1), R1 represents a C1-C20 alkyl group, an allyl group or an aralkyl group, L is an integer of 0 to 7, and n is an integer of 20 to 200.
Also, there has been proposed an inkjet recording method that does not cause color bleeding on recording medium with less or no ink absorbability (see, for example, JP-A No. 2007-136988).
Also, there has been proposed a formulation of ink containing a water-soluble organic solvent used in the present invention, where an amount of the water-soluble organic solvent is specifically defined (see, for example, JP-A No. 2009-138118).
The water-soluble organic solvent contained in the ink is generally used for improving moisture-retaining property and color saturation of images, and JP-A Nos. 2006-045436 and 2009-235233 use a water-soluble organic solvent used in the present invention. They do not describe which water-soluble organic solvent is effective for moisture-retaining property, or which water-soluble organic solvent is effective for improvement in color saturation of images.
Also, JP-A No. 2007-136988 utilizes UV irradiation and as a result a usable formulation of ink is limited, which makes an inkjet recording device complicated, leading to elevation of cost.
Also, in the ink disclosed in JP-A No. 2009-138118, a black ink and color inks are not satisfactory. When this ink is left to stand for a long period of time, adhesion of the ink to the head's repellent film easily occurs to tend to cause jetting failure.